Source: Nintendo: Wii U online functionality will be free | Joystiq Just like Steam & PSN, Nintendo Network will be free of charge.
Great that it will still be free, i just hope they have some half decent online system this time. A universal friends list and actually allowing people to communicate in games would be a great start... only really played Smash Bros / Maro Kart online on the Wii... might as well have been playing bots.
Nintendo still has a lot to improve so they can't really decide to charge people when their online gaming service somewhat sucked on the Wii, now it's time to get better so lets see how it turns out. It doesn't really bother me if they charge or not, what it matters is the quality of the service, if it's free but shit then I won't use it regardless of being free of charge.